How can I copy and paste dimensions to make objects the same size?
If you enable Align Tools Add-on in the Preferences(F4-&gt;P, or Edit -&gt; Preferences):

You will have Advanced button in the sidebar, Item tab:

You can then select the objects you want to scale, then select the one you wish to scale to so it's the last selected and active and hit Advanced under Advanced Align Operations:

In the Last Operation panel you will have Fit Dimensions: